The present invention relates to a method of separation of aromates from hydrocarbon mixtures of any aromate content by extractive distillation with a selective solvent.
More particularly, it relates to such a method in accordance with which the non-aromatic components of the hydrocarbon mixture which serves as an initial product are distillated off while the aromates together with the used solvents are withdrawn from the sump of the extractive distillation column and separated in a subsequent driving-out column in a distillative manner from the solvent. The aromates are withdrawn as a head product and the solvents as a sump product from the driving-out column, while the solvent is again reintroduced into the extractive distillation column.
During the utilization of the above mentioned method the maintenance of two conditions is necessary in practice. On the one hand, the non aromate content in the recovered aromates must not exceed a predetermined maximum value, and on the other hand the aromate losses must be as low as possible and the yield as high as possible. The fulfilling of this condition is however connected with certain energy consumption, since such extractive distillation processes are usually performed with the use of medium and high pressure vapor as an energy carrier. The medium pressure vapor serves first of all for heating the extractive distillation column, while the substantially more expensive high pressure vapor is required in the driving-out column for driving-out of the aromates from the solvent.
Due to the above described conditions, during the performance of a method of the above mentioned general type an economy of the energy cost must be taken in consideration when for recovering the energy consumption of the whole process, a part of the required high pressure vapor can be replaced by the less expensive medium pressure vapor.